Today, the farming of fish is a large and important industry. Traditionally, the farming takes place in sea-based installations, where the farming net cage has a seine of a given mesh size through which water flows freely.
The fish in these installations suffer from different diseases and salmon lice have lately been a great problem in connection with the farming of salmon. The lice get in through the net in the net cage installations. To avoid this problem of infection from pathogenic organisms (lice, algae, bacteria, virus, and so on) entering into the net cage, closed installations have been developed. Different land-based installations have been developed where the farming takes place in a tank on land and where fresh water is pumped from the sea and up into the installation. Furthermore, sea-based floating installations with watertight walls have also been developed. Such “watertight” walls are often made from a tarpaulin material, but they can also be of different moulded designs.
Such a farming net cage is described in the Norwegian patent NO332341, Ecomerden, and is a floating farming net cage with a double wall system, i.e. both a watertight outer wall and an internal seine. The net cage is fitted with a floating collar to ensure correct positioning when floating in the water and for the supply of fresh water to the net cage.